The \(c_0^{DVCS, \mathcal {I}}\) , and \((c,s)_1^{\mathcal {I}}\)  harmonics are dominated by twist-two GPD terms, although they do have twist-three admixtures that must be quantified by
the \(Q^2\) -dependence of each harmonic. The \((c,s)_1^{DVCS}\)  and \((c,s)_2^{\mathcal {I}}\)  harmonics are dominated by twist-three matrix elements, although the same twist-two GPD terms
also contribute (but with smaller kinematic coefficients than in the lower Fourier terms). The \((c,s)_2^{DVCS}\)  and \((c,s)_3^{\mathcal {I}}\)  harmonics
stem from twist-two double helicity-flip gluonic GPDs alone. They are formally suppressed by \(\alpha _s\)  and will be neglected here. They do not mix, however, with the twist-two quark amplitudes.
The exact expressions of these harmonics in terms of the quark Compton Form Factors (CFFs) of the nucleon are given in [1]}.
